The Marlins traded Ozuna to the Cardinals on the second-to-last day of the Winter Meetings, receiving four prospects in return: righthander Sandy Alcantara, outfielder Magneuris Sierra, righthander Zac Gallen and lefthander Daniel Castano.

Alcantara ranked was the Cardinals' No. 4 prospect and Sierra was their No. 7 prospect. Both made their major league debuts last season. Their additions beef up a Marlins farm system that entered the offseason among the worst in the game but has improved significantly as the franchise unloads veterans for prospects as part of their latest rebuild.

The Cardinals, meanwhile, add the impact bat they were looking for. After reaching a deal with the Marlins for Stanton that the slugger blocked with his no-trade clause, they were able to grab the two-time All-Star Ozuna, who has hit 60 home runs the past two seasons.

Alcantara becomes the Marlins new No. 1 prospect as a high-octane arm who has already reached the majors. A starter his entire minor league career, Alcantara pitched exclusively in relief as a September callup with the Cardinals, posting a 4.32 ERA with 10 strikeouts and six walks in 8.1 innings. Alcantara brings premium velocity with a fastball that sits 95-97 mph as a starter, 98-99 as a reliever and has been clocked as high as 102. He is still learning to harness that velocity. His heater is fairly straight and he tends to leave it over the plate, resulting in a lot of hard contact against it in both the majors and upper minors. When Alcantara tries to paint the corners he gets wild, leading to an elevated walk rate in spurts. It's a swing-and-miss fastball, though, when it's on. Alcantara has both an 82-84 mph curveball and 84-88 mph slider that tend to run together but flash above-average at their best, and his 89-91 mph changeup is plus at its best, but only about one in five he throws are competitive pitches. Alcantara's potential arsenal of a big fastball and 2-3 above-average secondaries is enticing, but all his offerings currently play down due to below-average command and a lack of consistency. If Alcantara can lock in his command as he matures, he could be an electric starter. Even if he doesn't, he can be a dominant end-of-game reliever.

Sierra impressed when he jumped straight from high Class A Palm Beach to the majors in 2017 when injuries decimated the Cardinals outfield and held his own. Over multiple stints with the Cardinals throughout the year he hit .317/.359/.317. Sierra projects as a plus-plus defender in center field and is an elite runner, with blazing raw speed that plays up with tight turns on the bases. He gets great jumps and takes excellent routes in center field, although he largely played corner outfield in his ML callups and was noticeably raw there. He has a plus arm that plays in any spot. No one doubts Sierra's speed and center field defense, but not all evaluators are convinced he will hit enough to be an everyday player in the modern game. Sierra is physically slight at 5-foot-11, 160 pounds and is largely a slap hitter who will only occasionally drive a ball into a gap. He doesn't walk much, and his combination of a likely low on-base percentage and zero power makes him a tough sell. Sierra cut his strikeout rate and puts the bat on the ball enough that optimistic evaluators believe he can eventually grow into a doubles and triples hitter who does just enough offensively to hold to down an everyday job with his speed and defense.

The Cardinals drafted Gallen out of North Carolina in the third round in 2016 and he shot through their system all the way to Triple-A by the end of his first full season. He 10-8, 2.93 overall, with 121 strikeouts and 35 walks in 147.2 innings. Gallen is a mature pitcher with superb command of a four-pitch arsenal, a bit of deception with a cross-fire delivery and advanced understanding of how to set hitters up. Gallen pounds the bottom of the strike zone with an 89-93 mph fastball, uses an 86-88 mph cutter as a particularly useful secondary and adds in an 82-85 mph changeup and 77-79 mph curveball that show average potential, although his curveball can get loopy and hang on him at times. Gallen mixes and matches all of his pitches, throws them all for strikes, works quickly and stays off the big part of the plate. He lacks a wipeout offering, but most evaluators believe he is a viable back-end starter in the big leagues, and soon.

The Cardinals drafted Castano in the 19th round out of Baylor in 2016 and he more than held his own at short-season State College in 2017, going 9-3, 2.57 in 14 starts, albeit as someone well older than league average. Castano is a pitchability lefty with an 88-92 mph fastball he mixes with a cutter and curveball. He sequences his pitches well, throws strikes and doesn't hurt himself with mistakes. Castano will have to prove his stuff plays in full-season ball before evaluators bite fully, and he projects to get that chance in low Class A Greensboro's rotation to start 2018.

Often overshadowed by his teammate Stanton, Ozuna had a power outburst of his own last year, hitting .312 with 37 homers, 124 RBIs and a .924 OPS. He adds significant thump to a Cardinals lineup that had no one hit more than 25 home runs last year. Ozuna primarily played left field for the Marlins and won his first career Gold Glove last season, leading all National League left fielders in putouts (305) and fielding percentage (.984) and finishing second with 10 assists. He is arbitration-eligible the next two seasons and is scheduled to become a free agent in 2020. As a premier-hitting, Gold Glove-winning outfielder, Ozuna stands to play a starring role for the Cardinals as long as he's there.